When and how to use fertilizers

Plants have two basic needs: light and water. However, the process that allows them to synthesize their food through photosynthesis actually requires the intervention of a number of micronutrients, which we take for granted because they are usually found naturally in the substrate. But the soil does not spontaneously generate these nutrients, which end up being exhausted at some point, which is why the use of fertilizer is essential. In short, fertilisers provide a series of nutrients to the soil so that they can be absorbed by plants and contribute to their development, growth and splendor.

Before you go into a frenzy of fertilizing all your plants so that they become lush and you end up killing them by excesses, it's imperative that you understand when and how to use fertilizer. Don't worry, it's less complex than you think, and you'll learn all the tricks to feed your plants at the right time. With these tips I assure you that your plants will become the envy of the neighborhood.

What is fertilizer?

According to the FAO, Food and Agriculture Organization of the United Nations, a fertilizer is any material that contains at least 5% of the basic nutrients needed by plants. These nutrients are Nitrogen (N), Phosphorus ℗ and Potassium (K). This material returns to the soil all the nutrients that have been absorbed by plants, but also supports the development, growth and formation of fruits and flowers.

You need to know that fertilizers aren't a quick fix for all your plants' problems. It's not going to resurrect plants or make them grow faster or faster. Fertilizers only have one function and one utility depending on the specific need of each plant. If your plant is on the verge of death due to a cause other than a lack of nutrients (lack of water or too much sun, for example), fertilizer won't help it at all and can speed up its path to the other plane.

Also, not all fertilizers are suitable for all types of plants. There are species that have very specific needs, while others prefer poor soils. Learning these requirements and respecting them are key to obtaining plethoric plants and abundant harvests.

Types of Fertilizer

Simple

fertilizers

We could say that there are two types of fertilizers: simple and multinutrient. Simple ones are those that contain one of the main nutrients (nitrogen, phosphorus or potassium). This type of fertilizer is usually used in the agricultural field or on a large scale, as it is essential to know the crop and type of plant very well to find the perfect balance of nutrients to be used. Simple fertilizers include:

• Nitrogenates

: As the name suggests, they are responsible for providing nitrogen to the plant. This nutrient is responsible for stimulating the growth of the plant, making it greener and more abundant. Some of these are urea, ammonia, and ammonia nitrate among others. Urea is the fertilizer with the highest nitrogen content (46%), and it is also quite economical. Ammonium sulfate offers 21% nitrogen, while calcium ammonium nitrate has just over 27% nitrogen.

• Phosphorus

is responsible for providing phosphorus to plants. This micronutrient is linked to flowering, fruit production, and root development. A phosphorus fertilizer can be simple superphosphate (16 to 20% phosphorus) and triple superphosphate (46%).

• This

nutrient is responsible for protecting the plant from extreme temperatures, as well as improving the fertility of the substrate and transporting nutrients to the plant. An example of these fertilizers is potassium chloride, which is 60% potassium.

Multinutrient fertilizers

are those fertilizers that combine several primary nutrients. They are also known as NPK or NP fertilizers, depending on the type of nutrient it includes. This is the type of fertilizer that we usually buy to treat plants at home, because they offer a balance of nutrients from the factory and are very easy to use. It is important to learn how to choose this type of fertilizer, as this will allow you to acquire one suitable for each type of plant.

How to choose

• a multinutrient fertilizer To choose the fertilizer

, you must read the label. You will find 3 numbers in the format x-x-x. These numbers will indicate the percentage of nitrogen, phosphorus and potassium respectively. In other words, in a bag of 10Kg of 20-15-30 fertilizer you will have 2kg of Nitrogen, 1.5kg of phosphorus and 3kg of potassium. The rest of the ingredients will correspond to inert elements that act as a vehicle for the fertilizer.

Usually the manufacturer includes on the label the indications for the use of the fertilizer, as well as the plants that do well in that proportion

of nutrients; however, you can check in our plant guides what proportion the ideal fertilizers should have for that particular plant species. As a general rule of thumb, you can look for a fertilizer that has twice as much phosphorus as nitrogen and potassium, for example, 15-30-15 or 12-24-12.

Having this knowledge can even help you save money, as you can choose the perfect option even if it hasn't been labeled by the brand. Let me explain: sometimes manufacturers put higher prices on a product with a nice label, but that is exactly the same as another with a simpler presentation. If you can't find the right ratio for the type of plant you have, you can apply a trick: read the label of the specialty fertilizer and take note of the numbers, which you'll use to search for a generic one. For example, a special fertilizer for orchids has an NPK ratio of 30-10-10, so you can look for any fertilizer with these ratios for your orchids, even if the label doesn't specify it.

Signs That a plant needs Fertilizer

• The first step is to rule out other problems: watering, lighting, and humidity.
• The plant has small, yellow leaves. The leaves at the bottom turn yellow and the newer ones turn pale green. This happens when there is little nitrogen because this is what gives them their green color.
• The plant does not grow or have new leaves. If it also has yellow leaves, we may be facing a potassium deficiency.
• The older leaves are a very dark but dull green color that then changes to a reddish or purple hue, then dries out. This indicates a lack of phosphorus.
• If the leaves look yellowish in the center but the edge and veins are still green, it's because it lacks iron.
• When the edges of the leaves look yellowish and dry, it indicates a lack of potassium. It may resemble the symptoms of magnesium deficiency, but this affects new leaves more.
• The older leaves look yellow between the veins and edges, except for a green portion at the base. This is a sign that indicates magnesium deficiency.
• Check the lower shoots, which are the oldest. If they have any discoloration or problem, it indicates that they are missing some macroelement (NPK) but if the leaves with problems are the newest, which are located at the top, then what is missing are the microelements.
• If you've used fertilizers and these problems persist, it's because the high pH of the soil must be interfering with the absorption of the elements.

When to Use Fertilizers

Potted houseplants require a little more attention when it comes to fertilizers than those that are planted in the ground. This is because the roots are confined to a small space, they cannot spread as far as possible to reach nutrients, but have a limited amount in the substrate that is contained in the pot. On the other hand, there are substrate mixes that really have little soil, have more perlite and other materials that facilitate their drainage but do not have nutrients, on the other hand, many of these commercial substrates are sterilized, so they do not have the beneficial bacteria that can help the plant synthesize nutrients better.

Fertilizers should be used at the right time. Fertilizing a plant when the time isn't right can burn its roots or affect its growth. Although each species has its own preferences, the general rule of thumb is to do it during spring and/or summer, as this is the growing season for plants. Fertilizing in winter is unnecessary and can disturb the balance of the plant, as it is the resting season.

Houseplants can be fertilized once a month with liquid fertilizer during spring, summer, and early fall. outdoor plants have their own particular needs, especially those that bear fruit and are planted directly in the ground. Try to apply the fertilizer during the cooler time of day, so that the roots can better absorb the nutrients.

How to Use Fertilizers

The use of fertilizers will depend on the type. There is only one valid tip: read the manufacturer's label and follow the instructions. Every brand is different, concentrations change. Not all liquid fertilizers are used equally, so it's best to always read the label and follow the directions. Don't improvise because you can kill your plants. That said, it's important to know that fertilizers come in 3 different forms:

• Liquid fertilizer: Mix with the irrigation water in the watering can, following the manufacturer's instructions. Their effect is very fast, so they have a short effect and should be reapplied frequently; However, because they are easy to use and so fast, they are very popular.
  
  
  

  Liquid fertiliser for green plants

  Rich in iron and nitrogen

  14.00 €
• Granular fertiliser: It is spread in the substrate and acts with the irrigation water. They dissolve easily and should be applied a little less often than liquids.
  
  
  

  Nitroflower Fertiliser 750gr

  Slow-release fertiliser

  14.00 €
• Extended-release fertilizers: These come in the form of solid sticks or tablets that are buried near the roots of plants. They dissolve very slowly with each watering, offering nutrients at a steady rate.
  
  
  

  Plant Food Fertiliser

  Organic Fertiliser

  10.00 €

In Spring you can start when the days start to get longer and the temperatures start to rise, as these environmental changes take them out of their resting state. Try not to apply the fertilizer with the concentration indicated by the manufacturer, it is better to dilute it by half during the first 3 doses. This is because the plants are just waking up from winter, starting their growth cycle, and don't require as much fertilizer.

In summer you can start fertilizing on a regular basis. The frequency of application will depend on the type of fertilizer you're using. For example, liquid fertilizers should be applied every two weeks at least; while granules are used once a month or once every two months. Extended-release drugs last much longer, so depending on the manufacturer's indication, they should be applied every 3 to 4 months.

In Autumn, before the temperatures drop, you should decrease the amount and frequency of fertilizer. You can use half of what the manufacturer says 3 or 4 uses before the start of winter. In winter you should not fertilize, unless you live in a place with temperate temperatures or where there are not many temperature changes; However, at this time you should use half the fertilizer and decrease the frequency by half as well. If you live in the tropics, you should fertilize your plants as if they were always in summer.

The keys to achieving good fertilization are to apply little fertilizer more frequently and dilute the fertilizer very well, in addition to never applying it to plants that are excessively dry, better to water before. Also, avoid applying to plants that are under stress or that you have just transplanted. It's best to put a little less than the recommended fertilizer and go from there to adjust the doses, especially when it comes to liquid or granule fertilizers, as it's easy to overdo it and burn the plant.